1. Field of the Invention
Cable marking devices.
2. Prior Art
Various devices have been proposed in the prior art for marking cables and specifically devices for putting length markings on the plastic covering of the electric cables by marking meters, feet, or yards at precise locations on the jacket of the cable. It is found in the prior art that it is advantageous to measure the running length of the cable at a location prior to extrusion of the plastic jacket by accurately determining the length of the core and using that length measurement to operate a cable marker positioned immediately following the extruder so that the length mark is applied to the jacket of the cable while the jacket of the cable is still soft. In published German application 1,465,840, such a device is disclosed wherein the length measurement of the cable is carried out in front of the screw extruder by means of two measuring wheels which are in contact with the core so as to be rotated by the cable core. The measuring result of the two measuring wheels is mechanically or electrically transmitted to the marking apparatus. There are two outstanding disadvantages to the device illustrated in published German application 1,465,840 insofar as length marking is concerned. One is that the measuring results are obtained in front of the extruder. Thus at the end of the cable when there is no cable core between the measuring wheels no measuring data is obtained and transmitted. Consequently no markings are produced on the end of the cable. Another disadvantage comes about because the length is measured on the cable core which in most cases is not sufficiently uniform and therefore provides no accurate measuring data which is a prerequisite of accurate cable marking.
Other proposals include U.S. Pat. Nos. 3,552,308; 2,739,528; 3,711,757; and 3,788,312. Each of the referenced U.S. patents performs a similar operation but utilizes different structure and has disadvantages which the device of this invention overcomes.